Heat exchanger having convoluted fin end and method of assembling the same

ABSTRACT

The present invention provides a heat exchanger for transferring heat between a first working fluid and a second working fluid. The heat exchanger can include a corrugated fin positionable along a flow path of the first working fluid between adjacent tube walls and being operable to increase heat transfer between the first working fluid and the second working fluid. The fin can include a leg defined between adjacent folds. The heat exchanger can also include a plurality of convolutions extending inwardly from a distal end of the leg and terminating at different distances from the end.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 12/061,191, filed Apr. 2, 2008, and is also acontinuation-in-part of PCT Patent Application Serial NumberPCT/US2008/051747, filed Jan. 23, 2008, which claims priority to U.S.Provisional Application Ser. No. 60/881,919 filed Jan. 23, 2007, theentire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to heat exchangers and more particularly,to a fin for an exhaust gas recirculation cooler and a method of formingthe same.

SUMMARY

In some embodiments, the present invention provides a heat exchanger fortransferring heat between a first working fluid and a second workingfluid. The heat exchanger can include a pair of spaced apart headers, anumber of tubes extending between the pair of headers and providing aflow path for the first working fluid and being positioned along a flowpath for the second working fluid, and a fin supportable in one of thetubes and having a fold extending in a direction substantially parallelto a length of the one of the tubes between the pair of headers. The fincan include a number of recesses extending into and spaced along thefold.

The present invention also provides a heat exchanger for transferringheat between a first working fluid and a second working fluid includinga pair of spaced apart headers, a number of tubes extending between thepair of headers and providing a flow path for the first working fluidand being positioned along a flow path for the second working fluid, anda fin supportable in one of the tubes and having a fold extending in adirection substantially parallel to the flow path for the first workingfluid through the tubes. The fold can define first and second legs ofthe fin. A recess can be formed on the first leg and a protrusion can beformed on the second leg opposite to the recess on the first leg.

In some embodiments, the present invention provides a heat exchanger fortransferring heat between a first working fluid and a second workingfluid including a pair of spaced apart headers, a number of tubesextending between the pair of headers and providing a flow path for thefirst working fluid and being positioned along a flow path for thesecond working fluid, and a fin supportable in one of the tubes andhaving a serpentine fold extending in a direction substantially parallelto a length of the tube between the pair of headers.

The present invention also provides a heat exchanger for transferringheat between a first working fluid and a second working fluid includinga corrugated fin positionable along a flow path of the first workingfluid between adjacent tube walls and operable to increase heat transferbetween the first working fluid and the second working fluid. The fincan include a leg defined between adjacent folds and a plurality ofconvolutions extending inwardly from a distal end of the leg andterminating at different distances from the end.

In some embodiments, the present invention provides a corrugated fin fora heat exchanger, the heat exchanger having a flow path of a firstworking fluid and a flow path of a second working fluid and beingoperable to transfer heat between the first and second working fluids.The fin can include a leg defined between adjacent folds andpositionable along the flow path of the first working fluid and aplurality of convolutions extending inwardly from a distal end of theleg and having different lengths in the direction of the flow of thefirst working fluid along the flow path.

The present invention also provides a method of forming a heat exchangerfor transferring heat between a first working fluid and a second workingfluid. The method can include the acts of corrugating a fin to define aplurality of legs and forming a plurality of convolutions along one ofthe plurality of legs, the plurality of convolutions extending inwardlyfrom a distal end of the leg and terminating at different distances fromthe end.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a bottom perspective view of a heat exchanger according tosome embodiments of the present invention.

FIG. 2 is a partially cut-away view of a portion of the heat exchangershown in FIG. 1.

FIG. 3 is an exploded perspective view of a portion of a tube and a finof the heat exchanger shown in FIG. 1.

FIG. 4 is a perspective view of a portion of the fin shown in FIG. 3.

FIG. 5 is an exploded perspective view of a portion of a tube and a finaccording to an alternate embodiment of the present invention.

FIG. 6 is a perspective view of a portion of the fin shown in FIG. 5.

FIG. 7 is a top view of a partially formed fin that can be manufacturedaccording to the method shown in FIG. 9.

FIG. 8 is a perspective view of a partially formed fin that can bemanufactured according to the method shown in FIG. 10.

FIG. 9 illustrates a method for forming the fin shown in FIG. 5.

FIG. 10 illustrates another method for forming the fin shown in FIG. 5.

FIG. 11 is a perspective view of a section of the fin forming deviceshown in FIG. 10.

FIG. 12 is a perspective view of a portion of a heat exchanger finaccording to some embodiments of the present invention.

FIG. 13 is a perspective view of a portion of a heat exchanger finaccording to some embodiments of the present invention.

FIG. 14 is a perspective view of a portion of a heat exchanger finaccording to some embodiments of the present invention.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having” and variations thereof herein ismeant to encompass the items listed thereafter and equivalents thereofas well as additional items.

Unless specified or limited otherwise, the terms “mounted,” “connected,”“supported,” and “coupled” and variations thereof are used broadly andencompass both direct and indirect mountings, connections, supports, andcouplings. Further, “connected” and “coupled” are not restricted tophysical or mechanical connections or couplings.

Also, it is to be understood that phraseology and terminology usedherein with reference to device or element orientation (such as, forexample, terms like “central,” “upper,” “lower,” “front,” “rear,” andthe like) are only used to simplify description of the presentinvention, and do not alone indicate or imply that the device or elementreferred to must have a particular orientation. In addition, terms suchas “first” and “second” are used herein for purposes of description andare not intended to indicate or imply relative importance orsignificance.

FIGS. 1-4 illustrate a heat exchanger 10 according to some embodimentsof the present invention. In some embodiments, including the illustratedembodiments of FIGS. 1-4, the heat exchanger 10 can operate as anexhaust gas recirculation cooler (EGRC) and can be operated with theexhaust system and/or the emission system of a vehicle. In otherembodiments, the heat exchanger 10 can be used in other (e.g.,non-vehicular) applications, such as, for example, in electronicscooling, industrial equipment, building heating and air-conditioning,and the like. In addition, it should be appreciated that the heatexchanger 10 of the present invention can take many forms, utilize awide range of materials, and can be incorporated into various othersystems.

During operation and as explained in greater detail below, the heatexchanger 10 can transfer heat from a high temperature first workingfluid (e.g., exhaust gas, water, engine coolant, CO₂, an organicrefrigerant, R12, R245fa, air, and the like) to a lower temperaturesecond working fluid (e.g., water, engine coolant, CO₂, an organicrefrigerant, R12, R245fa, air, and the like). In addition, whilereference is made herein to transferring heat between two workingfluids, in some embodiments of the present invention, the heat exchanger10 can operate to transfer heat between three or more fluids.Alternatively or in addition, the heat exchanger 10 can operate as arecuperator and can transfer heat from a high temperature location of aheating circuit to a low temperature location of the same heatingcircuit. In some such embodiments, the heat exchanger 10 can transferheat from a working fluid traveling through a first portion of the heattransfer circuit to the same working fluid traveling through a secondportion of the heat transfer circuit.

As shown in FIGS. 1 and 2, the heat exchanger 10 can include a firstheader 18 and a second header 20 positioned at respective first andsecond ends 22, 24 of a stack of heat exchanger tubes 26 having outersurfaces 28 (shown in FIGS. 1, 3, and 5). In the illustrated embodimentof FIGS. 1-4, the first end 22 is secured to a first collecting tank 30and the second end 24 is secured to a second collecting tank 32. Inother embodiments, the heat exchanger 10 can include a single header 18and/or a single tank 30 located at one of the first and second ends 22,24 or at another location on the heat exchanger 10.

As shown in FIGS. 1 and 2, each of the tubes 26 can be secured to thefirst and second headers 18, 20 such that a first working fluid flowingthrough the heat exchanger 10 is maintained separate from a secondworking fluid flowing through the heat exchanger 10. More specifically,the heat exchanger 10 defines a first flow path (represented by arrows34 in FIG. 1) for the first working fluid and a second flow path(represented by arrows 36 in FIG. 1) for a second working fluid, and thefirst and second flow paths 34, 36 are separated such that the firstworking fluid is prevented from entering the second flow path 36 andsuch that the second working fluid is prevented from entering the firstflow path 34.

In some embodiments, such as the illustrated embodiment, the tubes 26are secured to the first and second headers 18, 20 and the first andsecond tanks 30, 32 such that the first working fluid enters the heatexchanger 10 through a first inlet aperture 40 in the first tank 30,travels through the tubes 26 of the heat exchanger 10 along the firstflow path 34, and is prevented from entering the second flow path 36. Inthese embodiments, the tubes 26 can be secured to the first and secondheaders 18, 20 and the first and second tanks 30, 32 such that thesecond working fluid enters the heat exchanger 10 through a second inletaperture 42 in the second tank 32, travels through the heat exchanger 10along the second flow path 36 between the tubes 26, and is preventedfrom entering the first flow path 34.

In other embodiments, the tubes 26 can have other orientations andconfigurations and the first and second flow paths 34, 36 can bemaintained separate by dividers, fins, partitions, and the like. Instill other embodiments, the first flow path 34 can extend through someof the tubes 26 while the second flow path 36 can extend through othertubes 26.

As shown in FIG. 2, the headers 18, 20 can have apertures sized toreceive one or more of the tubes 26. As illustrated by FIGS. 1 and 2,the first working fluid flowing along the first flow path 34 can enterthe tubes 26 through apertures formed in the first header 18. In theseembodiments, the first header 18 can also direct the second workingfluid from the second inlet aperture 42 between adjacent tubes 26 andcan prevent the second working fluid from flowing into the tubes 26. Thefirst header 18 can also prevent the first working fluid from flowingbetween the tubes 26.

In the illustrated embodiment, the heat exchanger 10 is configured as across-flow heat exchanger such that the first flow path 34 or a portionof the first flow path 34 is opposite to the second flow path 36 or aportion of the second flow path 36. In other embodiments, the heatexchanger 10 can have other configurations and arrangements, such as,for example, a parallel-flow or a counter-flow configuration.

In the illustrated embodiment, the heat exchanger 10 is configured as asingle-pass heat exchanger with the first working fluid traveling alongthe first flow path 34 through at least one of a number of tubes 26 andwith the second working fluid traveling along the second flow path 36between adjacent tubes 26. In other embodiments, the heat exchanger 10can be configured as a multi-pass heat exchanger with the first workingfluid traveling in a first pass through one or more of the tubes 26 andthen traveling in a second pass through one or more different tubes 26in a direction opposite to the flow direction of the first working fluidin the first pass. In these embodiments, the second working fluid cantravel along the second flow path 36 between adjacent tubes 26.

In yet other embodiments, the heat exchanger 10 can be configured as amulti-pass heat exchanger with the second working fluid traveling in afirst pass between a first pair of adjacent tubes 26 and then travelingin a second pass between another pair of adjacent tubes 26 in adirection opposite to the flow direction of the second working fluid inthe first pass. In these embodiments, the first working fluid can travelalong the first flow path 34 through at least one of the tubes 26.

In the illustrated embodiment, the heat exchanger 10 includes seventubes 26, each of which has a substantially rectangular cross-sectionalshape. In other embodiments, the heat exchanger 10 can include one, two,three, four, five, six, eight, or more tubes 26, each of which can havea triangular, circular, square or other polygonal, oval, or irregularcross-sectional shape.

As mentioned above, in some embodiments, the second flow path 36 or aportion of the second flow path 36 can extend across the outer surface28 of one or more of the tubes 26. In some such embodiments, ribs 56(see FIG. 3) can be formed along the outer surfaces 28 of the tubes 26to at least partially define channels 58 between adjacent tubes 26.Alternatively, as shown in FIG. 5, the tubes 26 of the heat exchanger 10can be generally oval shaped (i.e., a simple extruded tube) and devoidof ribs 56 defining channels 58. A housing can be provided around thetubes 26 to prevent the second fluid from leaking out of the heatexchanger 10 between adjacent tubes 26. In such an embodiment, thehousing would define the second flow path 36 between/around the tubes26.

In embodiments, such as the illustrated embodiment of FIGS. 1-4, havingoutwardly extending ribs 56, the ribs 56 of each tube 26 can be securedto an adjacent tube 26. In some such embodiments, the ribs 56 of onetube 26 can be soldered, brazed, or welded to an adjacent tube 26. Inother embodiments, adjacent tubes 26 can be secured together withinter-engaging fasteners, other conventional fasteners, adhesive orcohesive bonding material, by an interference fit, etc. In addition, ahousing can be provided around the tubes 26 of the embodimentillustrated in FIGS. 1-4.

Additional elevations, recesses, or deformations 64 can also oralternatively be provided on the outer surfaces 28 of the tubes 26 toprovide structural support to the heat exchanger 10, prevent thedeformation or crushing of one or more tubes 26, maintain a desiredspacing between adjacent tubes 26, improve heat exchange between thefirst and second working fluids, and/or generate turbulence along one orboth of the first and second flow paths 34, 36.

The heat exchanger 10 can include fins 66, which improve heat transferbetween the first and second working fluids as the first and secondworking fluids travel along the first and second flow paths 34, 36,respectively. The fins 66 can provide the heat exchanger core (i.e., thetubes 26) with increased surface area for distribution of the heatprovided by the first and/or second working fluids. As shown in FIGS. 2,3, and 5, the fins 66 can be positioned in the tubes 26. Alternativelyor in addition, fins 66 can be positioned between adjacent tubes 26. Inother embodiments, fins 66 can be integrally formed with the tubes 26and can extend outwardly from the outer surfaces 28 of the tubes 26, oralternatively, inwardly from inner surfaces 38 of the tubes 26. In someembodiments, the fins 66 can improve the durability and strength of theheat exchanger 10. The configurations (geometrical and topographical) ofthe fins 66 can be such that the expansion and contraction experiencedby the material due to thermal fluctuations can be compensated for withincreased flexibility (discussed in further detail below).

In the illustrated embodiment of FIG. 2, a fin 66 is supported in eachof the tubes 26, and extends along the entire length or substantiallythe entire length of each of the tubes 26 between opposite ends 68 ofthe tubes 26. As FIG. 2 illustrates, the fin 66 can also oralternatively extend across the entire width or substantially the entirewidth of each of the tubes 26 between opposite sides of the tubes 26. Inother embodiments, a fin 26 can be supported in only one or less thanall of the tubes 26, and the fin(s) 66 can extend substantially theentire length of the tube(s) 26 between opposite ends 68 of the tube(s)26, or alternatively, the fin(s) 66 can extend through the tube(s) 26along substantially less than the entire length of the tube(s) 26. Instill other embodiments, two or more fins 66 can be supported by or ineach tube 26. In some embodiments, the fins 66 can be secured to thetubes 26. In some such embodiments, the fins 66 are soldered, brazed, orwelded to the tubes 26. In other embodiments, the fins 26 can beconnected to the tubes 26 in another manner, such as, for example, by aninterference fit, adhesive or cohesive bonding material, fasteners, etc.

In some embodiments, the ends 68 of the tubes 26 can be press-fit intoone or both of the first and second headers 18, 20. In some suchembodiments, the ends 68 of the tubes 26 and the fins 66 supported inthe tubes 26 or between the tubes 26 can be at least partially deformedwhen the tubes 26 and/or the fins 66 are press-fit into the first and/orsecond headers 18, 20. As such, the tubes 26 and/or the fins 66 arepinched and maintained in compression to secure the tubes 26 and/or thefins 66 in a desired orientation and to prevent leaking. In someembodiments, the tubes 26 can be brazed, soldered, or welded to thefirst and/or second headers 18, 20.

In the illustrated embodiments, roll-formed sheets of metal are foldedto form the fins 66 in a method that will be described in further detailbelow. In other embodiments, the fins 66 can be cast or molded in adesired shape and can be formed from other materials (e.g., aluminum,copper, iron, and other metals, composite material, alloys, and thelike). In still other embodiments, the fins 66 can be cut or machined toshape in any manner, can be extruded or pressed, can be manufactured inany combination of such operations, and the like.

As most clearly shown in FIGS. 3 and 7, the fin 66 can be corrugated andhave an overall length L, width W, and height H. The length L of the fin66 is defined as the general direction of fluid flow within the tube 26(i.e., from the first header 18 to the second header 20). As shown inthe embodiment illustrated in FIG. 3, each fold forms a serpentine spine76 that extends generally in parallel to the length L of the fin 66.

The illustrated embodiment of the fin 66 includes a series ofparallel-running spines 76 that form alternating peaks 78 and valleys 80along the width W of the fin 66. As shown in FIG. 2, the peaks 78 andvalleys 80 can engage respective upper and lower interior sides (e.g.,between upper and lower sides in FIGS. 2, 3, and 5) of a tube 26. In theillustrated embodiment, legs or flanks 82 extend between each pair ofadjacent folds (i.e., from a peak 78 to a valley 80 or vice versa) alongthe length L, to give the fin 66 a height H. In addition, the fins 66 ofsome embodiments can have pointed, squared, or irregularly shaped peaks78 and/or valleys 80. The resulting lateral edge of the fin 66 of theillustrated embodiment, as shown in FIGS. 2 and 3 can be generally wavy.However, in other embodiments, the lateral edge can be generallysinusoidal or saw-toothed, among other shapes. The structural elementsformed by each fold 76 of the corrugated fin 66 are described morespecifically with reference to FIGS. 4 and 6 below.

As illustrated by FIGS. 4 and 6, a first leg 82 a can be at leastpartially defined on one side of a spine 76 and a second leg 82 b can beat least partially defined on the other side of the spine 76. Fold 76 ais positioned immediately adjacent to the first leg 82 a and defines aheight h of the leg 82 a. Similarly, fold 76 b is positioned at thedistal end of the second leg 76 b, which has the same height h. Thespace S between adjacent legs 82 a, 82 b is defined as the distancebetween the points located at the same distance along length L andheight h of each leg 82. The legs 82 of the fin 66 can also have varioustopographical configurations. For example, at one point along the lengthL, the legs 82 can be convoluted or wavy (i.e., when viewed from an endof the fin 66, and at another point along the length L, the legs 82 canbe straight.

As shown in FIGS. 3-8, the legs 82 can include contour elements such asrecesses 86 and protrusions 88 spaced along their length L. Theseelements are deformations in the material that forms the fin 66 and donot pierce or provide connections between opposite sides of the fin 66.In some such embodiments, a recess 86 formed on one side of a leg 82 canconsequently form a protrusion 88 on the opposite side of the leg 82(i.e., a recess 86 is a geometric complement of protrusion 88). Thecontour elements formed in the fin 66 can appear as pyramid, frustum,prism, and/or hemispheroid-like projections or recesses, among others.In the illustrated embodiment, the contour elements each have two planesof symmetry (one of which is the length L, space s plane, and the otherof which is the height h, space s plane). As such, the upper half of thecontour element is a mirror image of the bottom half (with respect tothe height h of the leg 82 it is positioned on). Similarly, the lefthalf of the contour element is a mirror image of the right half (withrespect to the length L of the leg 82 it is positioned on). In someembodiments, a protrusion 86 in one leg 82 a can be positioned such thatit is at least partially receivable in a recess 88 in an adjacent leg 82b (i.e., at the same distance along height h and length L of each leg).

In some embodiments, contour elements can extend along the entire heighth of the leg 82 from one fold 76 to an adjacent fold 76 (i.e., from apeak 78 to an adjacent valley 80 or vice versa). Each contour elementhas a width d, as shown in FIG. 6. In the illustrated embodiment, thewidth d also indicates the spacing between similar contour elements. Inother embodiments, the spacing between similar contour elements can begreater than the width d of an intervening or alternating contourelement.

As shown in FIG. 4, the serpentine shape of the spine 76 is determinedby the geometry and placement of the recesses 86 and protrusions 88. Inthe illustrated embodiments, recesses 86 are alternated with protrusions88 along the length L of each leg 82, and each of the contours extendsbetween adjacent folds 76. Accordingly, a number of recesses 86 and anumber of protrusions 88 can be spaced along the edge of each fold 76.FIG. 4 includes reference measurements to more clearly illustrate thegeometry of the fin 66. Specifically, reference a indicates the distancebetween the midline of the fold 76 and the edge of a recess 86,reference b indicates the distance between the midline of the fold 76and the edge of a protrusion 88, and reference c indicates the lateraldistance (i.e., the direction normal to the length L of the fin andwidth d of the contour element) from the edge of the contour element atthe fold 76, to its outermost point/extension.

As illustrated in FIGS. 3-6, a fin 66 formed with longitudinal rows ofalternating contour elements 86, 88, can be folded such that the space Sbetween adjacent legs 82 at a particular height h can be generallyconstant along their length L. Thus, the flow path cross-sectional areais essentially constant along the length L between opposite ends 68 ofthe tube 26. Accordingly, the first flow path 34 is made circuitous andis consequently longer than a straighter flow path. Such a finconfiguration can increase turbulence of the working fluid andconsequently allow for more efficient heat transfer without causingsignificant pressure changes/buildup along the length L of the fin 66.Additionally, contour elements formed in the fins 66 can impact theshape of the spine 76. For example, FIGS. 3-8 show how a pattern ofrecesses 86 and protrusions 88—specifically longitudinal rows of thecontinuously alternating contour elements—can create a serpentine-shapedspine 76. As such, even the flow path immediately adjacent to the innersurfaces 38 of the tube 26 is elongated and made circuitous. Theserpentine shape of the spine 76 can also provide a reinforcedconnection between the tube 26 and the fin 66 which can also improveheat transfer.

In embodiments having fins 66 with wavy or contoured cross-sections,such as the illustrated embodiments, the fins 66 operate as elasticmembers to absorb or at least partially absorb vibrations and/or toabsorb expansions and contractions of the fins 66 caused by fluctuatingtemperatures of the first and/or second working fluids. In some suchembodiments, the elasticity of the contoured fins 66 prevents or reducescracking and breaking of the fins 66. Alternatively or in addition, theelasticity of the contoured fins 66 prevents and/or reduces cracking andbreaking of connections (e.g., solder points, braze points, weld points,etc.) between the spines 76 of the fins 66 and the interior sides of thetubes 26.

As shown in FIGS. 5-8, in some embodiments, contours 86, 88 can extendcontinuously from a first lateral edge 92 to a second lateral edge 94,along the length L of a leg 82. In other embodiments, such as thoseillustrated in FIGS. 2-4, contours only extend continuously along thelength L of a middle portion of the fin 66, while the edges 92, 94 havea different topographical configuration. For example, as shown in theembodiments of FIGS. 3 and 4, the convolutions of the fin 66 can startat a lateral edge 92 of a fin 66 and extend along the length L of thefin 66 a common distance, dc. In some embodiments, the convolutions canextend from a lateral edge of the fin 66 to a point beyond theconnection plane of the header 18, with the stack of tubes 26. Thecontoured portion can allow for changes in length L (i.e., longitudinalflexibility), while the convoluted edges can compensate for changes inheight h of the legs 82 (i.e., vertical flexibility). This can bedesirable in embodiments where the height of the fin H is constrained byconnection to the inner surfaces 38 of the tube 26, especially where thetube ends 68 are further constrained by the first and second headers 18,20.

FIGS. 12-14 represent an alternate embodiment of a heat exchanger fin266 according to the present invention. The portion of a heat exchangerfin 266 shown in FIGS. 6 and 7 is similar in many ways to theillustrated embodiments of FIGS. 1-8 described above. Accordingly, withthe exception of mutually inconsistent features and elements between theembodiment of FIGS. 12-14 and the embodiments of FIGS. 1-8, reference ishereby made to the description above accompanying the embodiments ofFIGS. 1-8 for a more complete description of the features and elements(and alternatives and/or additions to the features and elements) of theembodiment of FIGS. 12-14. Features and elements in the embodiment ofFIGS. 12-14 corresponding to features and elements in the embodiments ofFIGS. 1-8 are numbered in the 200 series.

As illustrated in FIGS. 12-14, fin 266 can have convolutions 270extending from the lateral edges 292, 294 a distance, dc (i.e., parallelto length, L) along the leg 282 of the fin 266, in a direction parallelto the folds 276 that define the leg 282. In other embodiments,convolutions 270 can be positioned along the fin 266 at a location thatis not immediately adjacent a lateral edge 292, 294. Any number ofconvolutions 270 can be provided on a portion of leg 282, and the numberof convolutions 270 can be consistent or vary from leg portion to legportion (and/or from lateral edge 292 to lateral edge 294, and/or fromfin 266 to fin 266, etc.). In addition, the geometrical shape of theconvolutions 270 can vary from rounded to pointed. The number ofdiffering shape convolutions 270 can be consistent or vary from legportion to leg portion (and/or from lateral edge 292 to lateral edge294, and/or from fin 266 to fin 266, etc.). Further, as shown in theillustrated embodiment of FIG. 14, the height, hc of each convolution,the total convoluted height, cc (see FIG. 12) on a particular leg 282,and the height, hs of any space (area lying in the plane of leg 282)between convolutions 270 can be consistent or vary from leg portion toleg portion (and/or from lateral edge 292 to lateral edge 294, and/orfrom fin 266 to fin 266, etc.).

Convolutions 270 can include beads 272 and dimples 274 that alternatealong the height h of the fin 266. In general, a bead 272 is aconvolution 270 projecting in one direction from the plane of a leg 282(defined by a point adjacent each of the folds defining the leg and oneother point on the leg 282), while a dimple 274 is a convolutionprojecting in the opposite direction from the plane of a leg 282. Inorder to clarify the following explanation, the following namingconvention will be followed: when the surface of any particular leg 282is viewed, beads 272 will extend away from the viewer while dimples 274will extend toward the viewer. As such, it should be understood that twoor more dimples 274 could be positioned adjacent each other (as couldtwo or more beads 272).

FIGS. 12-14 illustrate that convolutions 270 on a single leg 282 canextend varying distances, dc along the length L of the fin 266. Forexample, in FIG. 12, the uppermost convolution, dimple 274, extends fromlateral edge 292 of the fin 266 a distance, dc less than the adjacentconvolution, bead 272 (immediately below the uppermost convolution).Further, two non-adjacent convolutions 290 can extend the same distance,dc (i.e., have the same length)-dimples 274 in FIG. 12 or dimple 274 andbead 272 in FIG. 13 for example. In other embodiments two or moreadjacent convolutions 270 can extend the same distance, dc along thelength L of the leg. In addition, the lengths of correspondingconvolutions 270 (i.e., convolutions at the same height h—for example,274 a and 274 b in FIG. 14) on adjacent legs 282 can be different orsimilar depending on the embodiment of the invention.

Alternatively or in addition, convolutions 270 can extend to differentendpoints with respect to contour elements 286, 288. For example, inFIG. 12, the middle convolution, bead 272, extends from lateral edge 292of the fin 266 into the protrusion 288 most proximal to the lateral edge292. In such embodiments, adjacent ends of two of the convolutions 270are oriented along, or intersected by, a line 296 which isnon-perpendicular to the flow of working fluid along the flow path. Asillustrated in the embodiment of FIG. 13, the uppermost convolution,bead 272, extends the farthest of all the convolutions on leg 282 a andterminates immediately adjacent the contour element, recess 286. Asillustrated in the embodiment of FIG. 14, the middle convolution 270extends to an end point a distance away from the protrusion 288 mostproximal to lateral edge 292.

In some embodiments of the present invention, spaces 284 (area lying inthe plane of leg 282) can be provided between convolutions 270 and/orbetween a convolution 270 and a fold 276. As illustrated in FIG. 12,space 284 is provided between the uppermost dimple 274 and peak 278. Inanother example illustrated in FIG. 13, space 284 is provided betweenthe lowermost bead 272 and valley 280.

It should be understood that any of the features or elements describedabove, particularly but not exclusively with respect to convolutions270, can be provided on any, all, or none of the fins 266 in a heatexchanger 210 and/or the portions of a heat exchanger fin 266 (leg 282,fold 276, lateral edge 292, 294, etc.). Further, convolutions 270 can beprovided on fins 266 having through-holes and/or cut outs in the leg 282of the fin 266 (such as disclosed in U.S. patent application Ser. No.11/367,611, hereby incorporated by reference), alternatively or inaddition to contour elements 286, 288. Contour elements 286, 288 can, insome embodiments, be isolated from (i.e., not extend into) the folds 276of the fin 266 as shown in FIGS. 12-14. Still further, convolutions 270can be provided on the legs of fins 266 having louvers, slits or notches(such as disclosed in U.S. patent application Ser. No. 11/015,159), acombination of such features, and/or having no contour elements 286, 288at all.

In embodiments having fins 266 with convolutions 270, such as theillustrated embodiments of FIGS. 3, 4, and 12-14, the fins 266 operateas elastic members to absorb or at least partially absorb vibrationsand/or to absorb expansions and contractions of the fins 266 caused byfluctuating temperatures of the first and/or second working fluids. Insome such embodiments, the elasticity of the contoured fins 266 in theregion of the convolutions prevents or reduces cracking and breaking ofthe fins 66 and/or cracking and breaking of connections (e.g., solderpoints, braze points, weld points, etc.) between the spines 276 of thefins 266 and the interior sides of the tubes 226. Further, in the casethat cracking does occur in such embodiments, a staggered profile 290(see FIG. 14) where the convolutions 270 terminate along the height h ofthe leg (distal from the lateral edges 292, 294 of the fin 266) canforce the crack to propagate a longer distance (in some cases followingthe profile 290) toward the connection points of the fin 266 with innersurfaces 238 of the tube 226) which can take longer to occur, thusextending the functional life of the heat exchanger 210. Alternativelyor in addition, a varied staggered profile 290 of convolutions 270adjacent legs 282 can cause cracks to propagate toward the innersurfaces 238 of the tube 226 at different positions along the length Lof the tube, reducing the tendency of the tube itself to crack (and/orthe extent of cracking), thereby preserving the isolation of first andsecond flow paths 234, 236 and extending the functional life of the heatexchanger 210.

FIG. 9 illustrates a method of forming a fin 66 for a heat exchanger 10according to some embodiments of the present invention. The methodinvolves roll-forming a pattern of recesses 86 and protrusions 88 into asheet of deformable heat conducting material 100 (e.g, aluminum, copper,bronze, and alloys including one or more of these metals). To clarifythe description, the process of contour formation is shown in FIG. 9(and discussed with reference to FIG. 9) as occurring in two distinctand consecutive steps for a particular longitudinally-located, lateralsection of the sheet. First, at the right-hand side of the figure,recesses 86 are roll-formed, then, to the left of that, protrusions 88are roll-formed. However, in practice, roll-formation of recesses 86 andprotrusions 88 can be executed simultaneously (as described andillustrated with respect to the alternative embodiments shown in FIGS.10 and 11 below). Whether the recesses 86 and protrusions 88 are formedconsecutively or simultaneously, the roll-formed fin 66 in FIG. 9 thenundergoes a folding process (right-hand side of the figure) to createspines 76. The steps discussed above can be incorporated into ahigh-speed assembly process which is described in more detail below.

As shown in FIG. 9, the method can make use of a firstcylindrically-shaped roller 102 having projections 104 positioned inlongitudinal rows along its curved exterior surface 106. The firstroller 102 can be rotated about its axis 108 as it makes contact with afirst side 110 of the sheet of deformable material 100, positionedtangentially with respect to the curved surface 106. The weight of thefirst roller 102 can be used to exert pressure on the deformablematerial such that the projections 104 form recesses 86 in the material100. In other embodiments, the sheet of material 100 can be forced intocontact with the roller 100 by other means to form recesses 86.

The shape and size of the projections 104 with respect to the thicknessof the sheet of material 100 can be such that the recesses 86 formed bycontact of projections 104 with the first side 110 of the sheet ofdeformable material 100 create their geometric complement on a secondside (not visible) of the sheet 100 which is opposite to the first side110. Thus, recesses 86 and protrusions 88 can be simultaneously formedon the first side 110 and an opposite second side of the sheet 100,respectively.

A second cylindrically-shaped roller 112 having projections 114positioned in longitudinal rows along its curved surface 116 can bepositioned adjacent to the opposite side of the sheet 100 from the firstroller 102. The second roller 112 can also be rotated about its axis 118as it makes contact with the second side of the sheet of deformablematerial 100, positioned tangentially with respect to the curved surface116. In this way, recesses 86 can be formed on the second side of thesheet 100, and corresponding projections 88 can be formed on the firstside 110.

The rollers 102, 112 can be formed by axially stacking cylindricaldisks, the boundaries of which are illustrated by dashed lines in FIG.9. In some embodiments, disks with various shaped projections 114 and/orcircumferential spacing between projections 114 can be assembled into aroller that will form fins 66 with different dimensions and geographies.Similarly, the disks can be circumferentially staggered to provide fins66 with more or less space between rows of contour elements, which canresult in wider or narrower spines 76. The rollers 102, 112 can bearranged with respect to each other such that the recesses 86 andprotrusions 88 on each side of the sheet are formed at specificlocations with respect to each other. For example, FIGS. 7-9 illustratehow the rollers 102, 112 can be aligned to form lateral and longitudinalrows of alternating recesses 86 and protrusions 88 along the sheet 100.The lateral rows are separated by narrow gaps where the sheet 100 can befolded to form corrugations such that the lateral rows become legs 82and the gaps become spines 76. In the illustrated embodiment, therollers 102, 112 are staggered slightly to form serpentine-shaped spines76. In other embodiments, the rollers 102, 112 can be aligned to formstraight spines 76. In still other embodiments, the positioning, size,and/or shape of the projections 104, 114 on the first and/or secondrollers 102, 112 can be varied to change the geometry and/or topographyof the fin 66. In still other embodiments, curved surfaces 106, 116 ofthe rollers 102, 112 can be provided with indentions corresponding(i.e., in location, size, shape, etc.) to the projections 114, 104 inthe opposing roller 112, 102, in order to better define the contoursformed in the sheet 100.

FIG. 10 illustrates a method of forming fins 66 according to anotherembodiment of the invention. The method illustrated in FIG. 10 usesstar-shaped rollers to simultaneously form contour elements andpartially fold the fin 66. A first star-shaped disk 120 represents afirst star-shaped roller that is positioned on a first side 110 of asheet of deformable material 100 in the illustrated embodiment of FIG.10. Along the circumference of the first disk 120, alternating ridges122 and crevasses 124 create the star shape of the disk. The ridges 122and crevasses 124 can contribute to the formation of peaks 78 andvalleys 80 as will be described in further detail below. Between eachridge 122 and crevasse 124 is formed a projection 126 or an indention128. The projections 126 and indentions 128 can form recesses 86 andprotrusions 88 in the fin as will also be discussed in further detailbelow. In some embodiments, such as the illustrated embodiment, theprojections 126 and indentions 128 can be geometric complements and havemultiple planes of symmetry as discussed previously with respect torecesses 86 and protrusions 88. In other embodiments, the ridges 122 canbe geometric complements of crevasses 124.

A second star-shaped disk 130 in FIG. 10 represents a second star-shapedroller that can have alternating ridges 132 and crevasses 134 thatseparate alternating projections 136 and indentions 138 similar (i.e.,in shape, size, etc.) to those of the first disk 120. Alternatively orin addition, the projections 136 can be geometric complements ofindentions 128 and projections 126 can be geometric complements ofindentions 138, in which case, projections 126, 136 need not begeometric complements of indentions 128, 138 on the same disk. Thesecond star-shaped disk 130 is positioned on a second side 140 of thesheet of material 100.

The first and second star-shaped disks 120, 130 can be positioned withrespect to each other such that each ridge 122 of the first disk 120fits within a crevasse 134 of the second disk 130 and each ridge 132 ofthe second disk 130 fits within a crevasse 124 of the first disk 120 asthe disks 120, 130 turn on their respective axes. Thus, when the sheetof deformable material 100 is fed between the star-shaped disks 120,130, the corresponding ridges 122 and crevasses 134 fold the material toform peaks 78, and corresponding ridges 132 and crevasses 124 fold thematerial to form valleys 80. Similarly, the projections 126, 136 andcorresponding indentions 138, 128 form recesses 86 and protrusions 88 inthe fin 66.

Star-shaped rollers can be made up of star-shaped disks 120 that arestacked axially, similar to the arrangement discussed above with respectto the embodiment of FIG. 9. FIG. 11 illustrates how these star-shapeddisks 120 can be stacked in an alternating arrangement such that aprojection 126 in one disk is positioned adjacent an indention 128 in asecond disk. Adjacent disks can be staggered such that the ridges 122and crevasses 124 in one disk are not in direct alignment with theridges 122 and crevasses 124 in a second disk, as shown in FIG. 11. Bycomplementary positioning of two star-shaped rolls having thisarrangement of disks, a fin 66 can be formed having serpentine spines76, as shown in FIGS. 3-8.

After the fins 66 have been roll-formed and folded, they can be cut tothe appropriate size and then fined into tubes 26. In other embodiments,the fins 66 can be cut before they are folded. Alternatively, the tubes26 can be assembled around the fins 66. In still other embodiments, thetubes 26 and the fins 66 can be cut to size simultaneously.

The embodiments described above and illustrated in the figures arepresented by way of example only and are not intended as a limitationupon the concepts and principles of the present invention. As such, itwill be appreciated by one having ordinary skill in the art that variouschanges in the elements and their configuration and arrangement arepossible without departing from the spirit and scope of the presentinvention.

What is claimed is:
 1. A corrugated fin for a heat exchanger, the heatexchanger having a flow path of a first working fluid and a flow path ofa second working fluid and being operable to transfer heat between thefirst and second working fluids, the fin comprising: a leg definedbetween adjacent folds and positionable along the flow path of the firstworking fluid; and a plurality of convolutions extending inwardly from adistal end of the leg, at least some of the plurality of convolutionshaving different lengths in the direction of the flow of the firstworking fluid along the flow path, wherein the plurality of convolutionsinclude three adjacent convolutions, and wherein two of the threeconvolutions have similar lengths in a direction substantially parallelto a spine formed between the leg and an adjacent leg.
 2. The corrugatedfin of claim 1, wherein at least one of the plurality of convolutionsterminates adjacent to a contour extending along the leg.
 3. Thecorrugated fin of claim 1, wherein at least two non-adjacent ones of theplurality of convolutions extend inwardly a common distance in thedirection of the flow of the first working fluid along the flow path. 4.The corrugated fin of claim 1, wherein the corrugated fin includes aplurality of adjacent legs, each of the plurality of adjacent legsincluding a plurality of convolutions extending inwardly from distalends of the legs and terminating at different distances from the ends inthe direction of the flow of the first working fluid along the flowpath.
 5. The corrugated fin of claim 1, wherein adjacent ends of atleast two of the plurality of convolutions are intersected by a linewhich is non-perpendicular to the flow of the first working fluid alongthe first flow path.
 6. The corrugated fin of claim 1, wherein the twoof the three convolutions are shorter than the other of the threeconvolutions in the direction substantially parallel to the spine. 7.The corrugated fin of claim 1, wherein the two of the three convolutionsare positioned on opposite sides of the other of the three convolutions.8. The corrugated fin of claim 1, wherein the two of the threeconvolutions are positioned adjacent each other.
 9. A corrugated fin fora heat exchanger, the heat exchanger having a flow path of a firstworking fluid and a flow path of a second working fluid and beingoperable to transfer heat between the first and second working fluids,the fin comprising: a leg defined between adjacent folds andpositionable along the flow path of the first working fluid; and aplurality of convolutions extending inwardly from a distal end of theleg and having different lengths in the direction of the flow of thefirst working fluid along the flow path, wherein the plurality ofconvolutions include at least three adjacent convolutions with a middleone of the convolutions having a greater length in a directionsubstantially parallel to a spine formed between the leg and an adjacentleg.
 10. A corrugated fin for a heat exchanger, the heat exchangerhaving a flow path of a first working fluid and a flow path of a secondworking fluid and being operable to transfer heat between the first andsecond working fluids, the fin comprising: a leg defined betweenadjacent folds and positionable along the flow path of the first workingfluid; and a plurality of convolutions extending inwardly from a distalend of the leg and having different lengths in the direction of the flowof the first working fluid along the flow path, wherein opposite ends ofthe leg are secured between tube walls and, in a region of connection ofthe tubes to a collecting tank, the convolutions are configured tocompensate for length changes in a stacking direction of the tubescaused by temperature changes.
 11. A corrugated fin for a heatexchanger, the heat exchanger having a flow path of a first workingfluid and a flow path of a second working fluid and being operable totransfer heat between the first and second working fluids, the fincomprising: a leg defined between adjacent folds and positionable alongthe flow path of the first working fluid; and a plurality ofconvolutions extending inwardly from a distal end of the leg and havingdifferent lengths in the direction of the flow of the first workingfluid along the flow path, further comprising a plurality of adjacentlegs, each of the plurality of adjacent legs including a plurality ofconvolutions extending inwardly from distal ends of the legs andterminating at a distance in the direction of the flow of the firstworking fluid along the flow path different than a correspondingconvolution of an adjacent leg.